draft stamp"Provisional, Subject to Revision"

Proceedings of the U.S. Geological Survey (USGS) Sediment Workshop, February 4-7, 1997

CONTINUOUS TURBIDITY MONITORS AT
TWO WEST VIRGINIA NAWQA SITES

Eychaner, James H.,
U.S. Geological Survey,
11 Dunbar Street,
Charleston, WV 25301

Continuous turbidity monitors were installed at two sites in West Virginia as part of data collection to assess inorganic chemical loads through both dissolved and suspended pathways from basins that include extensive coal mines. Turbidity, pH, specific conductance, and temperature have been monitored continuously at the sites (table 1) since December 1996, satellite data transmission began in January 1997, and data collection is planned through September 1998. The sites are among 12 routinely sampled since October 1996 by the Kanawha-New River basin study unit of the National Water Quality Assessment (NAWQA) program. Basic NAWQA samples are collected from the water column both monthly and during extreme flow conditions for major ions, nutrients, organic carbon, suspended sediment, and fecal bacteria; samples for metals, pesticides, and volatile organic compounds are added at some sites and dates. Bed sediment and fish tissue at the sites have been analyzed for organic compounds and metals.

table 1

The monitoring data are intended to identify the range of hydrologic and geochemical conditions at the sites in order to design a thoughtful sampling program for metal transport. Metal partitioning between the dissolved and sediment phases is expected to vary with pH and ionic strength, and metal transport is expected to vary with stream discharge and sediment concentration. Initially, samples of suspended sediment will be analyzed for concentration in the coarse and fine fractions in order to develop turbidity-concentration relations and estimate suspended-sediment load in each fraction (see Gippel, 1995; Lewis, 1996). If sediment loads can be estimated reliably, sampling for metal concentrations on the suspended sediment will be planned after the approach of Horowitz (1995) and compared to concentrations on bed sediment. Automated sampling is not presently planned.

Among anticipated difficulties are possible poor correlations between turbidity and total suspended-sediment concentration. Few studies have focused primarily on the transport and chemistry of fine-grained sediment. Turbidity measurements are not directly comparable between sites, in part because instruments are not well standardized as to light source and detector geometry. Difficulties with the field instruments are expected, and a rigorous quality-assurance plan for the monitors is being prepared. Finally, because most coal mined in the study area has low sulfur content and generally low acid-drainage potential, the range of geochemical conditions may be less than would be desired for a test of the methods.

References Cited

Gippel, C.J., 1995, Potential of turbidity monitoring for measuring the transport of suspended solids in streams: Hydrological Processes, vol. 9, p.83-97.

Horowitz, A.J., 1995, The use of suspended sediment and associated trace elements in water quality studies: International Association of Hydrological Sciences, Special Publication No. 4, 58 p.

Lewis, Jack, 1996, Turbidity-controlled suspended sediment sampling for runoff-event load estimation: Water Resources Research, vol. 32, no. 7, p. 2299-2310.

Autobiography

Eychaner, James H.,
U.S. Geological Survey,
Charleston, WV,

is presently NAWQA project chief for the Kanawha-New River Basin study unit and district water-quality specialist. He has been with the USGS Water Resources Division since 1974 in the Utah, Arizona, Hawaii, and West Virginia districts. His experience includes statistical flood-frequency analysis, indirect measurements of peak discharge, step-backwater flow routing, ground-water flow modeling, inorganic geochemistry of acidic drainage from copper mines in interacting arid-zone ground and surface waters, and PCB transport in humid-zone stream sediment.

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